Perhaps you should try some spelling variations:
thanh dai » thanh hai, thanh tai, thanh dat
qua ban » cua ban, qua quan
dua ban » dia ban, cua ban, mua ban
va chat » van chat, va phat, cao chat
sach lo » sach dao, sach doi, sach hoi
hieu va » lieu va, hieu qua
lang xa » lang ha, dang xay, lang van
cua tre » cua te, cuu tre, cua triet

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: thu ((sach lo) or (sac o)) lang xa hoi. hieu va chat ((dua ban) OR (qua ban)) thanh dai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu ((sach lo) OR (sac o)) lang xa hoi. hieu va chat ((dua ban) OR (qua ban)) thanh dai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu ((sach lo) or (sac o)) lang xa hoi. hieu va chat ((dua ban) OR (qua ban)) thanh dai cua tre".
• Adding a wildcard symbol may retrieve word variants: thu ((sach lo) or (sac o)) lang xa hoi. hieu va chat ((dua ban) OR (qua ban)) thanh dai cua tre*.